Hmm. I just created a fresh level and just watched the cows and the dung disappears after a minute. One thing that stops dung being removed is if it were picked up and dropped by the player or a bot. But that doesn't seem to be what's happening here. Does it disappear if you reload the level?
https://www.file-upload.net/download-12660694/neu.txt.html
does that work?
turned the game of for lunch, after lunch i saw the dung disappearing. 2nd time the savegame was loaded.
the cow problem on the north-earth field seems to be fixed. placed the cows on the bottom of the field and they'll "normally" moving to the top of the field. in 6.2 they getting stuck under the grass-free strip.